Primary structure of chicken skeletal muscle and fibroblast alpha-actinins deduced from cDNA sequences

The complete 897-amino-acid sequence of chicken skeletal muscle alpha-actinin and the 856-amino-acid sequence (97% of the entire sequence) of chicken fibroblast alpha-actinin have been determined by cloning and sequencing the cDNAs. Genomic Southern analysis with the cDNA sequences shows that skeletal and fibroblast alpha-actinins are encoded by separate single-copy genes. RNA blot analyzes show that the skeletal alpha-actinin gene is expressed in the pectoralis muscle and that the fibroblast gene is expressed in the gizzard smooth muscle as well as in the fibroblast. The deduced skeletal alpha-actinin molecule has a calculated Mr of 104 x 10(3), and each alpha-actinin can be divided into three domains: (1) the NH2-terminal highly conserved actin-binding domain, which shows similarity to the product of the Duchenne's muscular dystrophy locus; (2) the middle rod-shaped dimer-forming domain, which contains the spectrin-type repeat units; and (3) the COOH-terminal two EF-hand consensus regions. Comparison of the skeletal alpha-actinin sequence with the fibroblast and smooth muscle alpha-actinin sequences demonstrated that the EF-hand structure was conserved in all of these alpha-actinin sequences, despite the reported variability of the Ca2+ sensitivities of the actin-gelation by various alpha-actinin isoforms.     

A novel nonmuscle alpha-actinin. Purification and characterization of chicken lung alpha-actinin.

Two distinct alpha-actinin-like proteins were detected in chicken lung extract by immunoblot analysis with monoclonal antibodies against alpha-actinin. The mobilities of these proteins on SDS-polyacrylamide gel electrophoresis are very close (approximately 100 kDa). On SDS-polyacrylamide gel electrophoresis in the presence of 6 M urea, however, one of the proteins migrates at 115 kDa and is clearly separated from the other protein (105 kDa). The 115-kDa protein was purified and shown to have at least three unique amino acid sequences which were not detected in other kinds of alpha-actinins: one locates at the extreme NH2-terminal region, and the others locate at the COOH-terminal half region. Immunoblot and proteolytic cleavage analyses revealed that the 115-kDa protein has structural divergence at the COOH-terminal region that includes Ca(2+)-binding EF-hand motifs. Falling-ball viscometric studies showed that although the 115-kDa protein-induced gelation of F-actin is sensitive to Ca2+, the gelation activity of the 115-kDa protein is much higher than that of Ca(2+)-insensitive gizzard alpha-actinin regardless of Ca2+. This indicates that the 115-kDa protein is distinct from other nonmuscle alpha-actinins by its Ca2+ sensitivity.     

Enzymatic determination of phospholipase D activity with choline oxidase

A new enzymatic method was developed for the assay of phospholipase D [phosphatidylcholine phosphatidohydrolase EC 3.1.4.4] from cabbage leaves using choline oxidase from Arthrobacter globiformis cells. The method was based on the estimation of choline by the following series of enzymatic reactions after ending the phospholipase D reaction: Choline + 202 + h2o Choline oxidase Betaine + 2H2O2 2H2O2 + Phenol + 4-Aminoantipyrine Peroxidase Quinoneimine dye + 4H2O The amount of choline was proportional to the amount of resulting quinoneimine dye with an absorbance maximum at 500 nm. The phospholipase D reaction (choline liberation) was carried out at pH 5.5 in the presence of Ca2+ ions and ended by adding EDTA in conc. Tris-HCl buffer, pH 8, to give a final pH of around 8. The initial rate of the phospholipase D reaction was proportional to the enzyme concentration over the absorbance change range of 0 to 0.25 (equivalent to 0-21 micron of choline) under the optimal reaction conditions.     

Studies on interaction of oligopeptides with sodium dodecyl sulfate: Stopped-flow kinetics of chemical modification of tryptophan residues withN-bromosuccinimide

The stopped-flow kinetics of the reaction between oligopeptides containing tryptophan residues andN-bromosuccinimide (NBS) were studied in 50 mM sodium phosphate buffer (pH 7.0) containing sodium dodecyl sulfate (SDS). Decreases in the reaction rates attributable to the interaction between oligopeptides and SDS were observed, and oligopeptides studied were classified into types I and II on the basis of the interaction modes. Type I oligopeptides were dissolved in SDS micelles; type II oligopeptides interacted cooperatively with SDS monomers. The manner of interaction between SDS and oligopeptides of type II could be interpreted by a simple equilibrium relation: oligopeptide+n·(SDS)=oligopeptide·(SDS) _n .     

The stimulation of extracellular carbohydrases of edible mushrooms by the hot water-soluble fraction from corn fiber

Corn fiber (CNF) is an abundant by-product of the wet corn milling process in the production of cornstarch. We have shown that the hot water-soluble fraction (HWSF) from CNF has a promoting effect on the mycelial growth of various edible mushrooms, including mycorrhizal fungi. To reveal the promoting mechanisms, the effect of CNF-HWSF on the stimulation of extracellular enzymes was examined. The production of extracellular carbohydrases such as amylase, CMCase, and xylanase was markedly enhanced by the addition of low molecular weight fractions (less than MW 500) prepared from CNF-HWSF. The enzymatic stimulation and enhancement of mycelial growth appeared during 3–15 days after inoculation. Furthermore, a fraction of less than MW 500 was separated by gel filtrate chromatography into five fractions (A–E), and the effect of each fraction was investigated. Promoting effects were shown from C and D fractions; mycelial growth and enzyme production of Lentinula edodes were indicated although fraction D has no sugars and amino acids in CNF-HWSF. From these results, the promoting effect of CNF-HWSF seems to be a two-step reaction. The first step could be achieved by rich nutrients such as free amino acids and monosaccharides from CNF-HWSF. The second step (during 3–15 days) is considered to be that the marked promoting effect was caused by the stimulation of extracellular enzymes.